The present invention generally relates to power mesh schemes for a wire bond package. More specifically, the invention relates to a new mesh structure to support an L-shaped mesh structure and a T-shaped mesh structure which is an improvement to the L-shaped mesh structure.
As shown in FIG. 1, an L-shaped mesh structure 10 is used in connection with a vertical mesh structure 12. The L-shaped mesh structure 10 includes L-shaped power rails 14 arranged in quadrants of the mesh structure 10. An upper left quadrant 18, a upper right quadrant 20, a lower left quadrant 22, and a lower right quadrant 24 comprise the quadrants of the L-shaped mesh structure 10. Each L-shaped power rail 14 includes a vertical portion 14a and a horizontal portion 14b. This L-shaped mesh structure 10 realizes symmetrical current distributions even though only one layer is available for power distribution. To power the horizontal power rails, however, vertical trunks traversing the length of the die need to be inserted at a fixed pitch. Thus, the vertical mesh 12 which includes vertical power rails 26 is used in connection with the L-shaped mesh structure 10.
The center region of the L-shaped mesh structure is shown in FIG. 2. As shown in FIG. 2, an inner most VDD rail 28 positioned in the upper left quadrant 18 lies proximate to an inner most VDD rail 32 positioned in the lower left quadrant 22. Also an inner most VSS rail 30 positioned in the upper right quadrant 20 lies proximate an inner most VSS rail 34 positioned in the lower right quadrant 24. As a result, the distance, represented by the arrow 36, between the inner most VSS rail 38 of the upper left quadrant 18 and the inner most VSS rail 40 of the lower left quadrant 22, exceeds 200 xcexcm. Likewise, the distance, represented by the arrow 42, between the inner most VDD rail 44 of the upper right quadrant 20 and the inner most VDD rail 46 of the lower right quadrant 24, exceeds 200 xcexcm. These large distances will result in EM violations unless the number of vias is increased. Increasing the number of vias, however, is not a desired approach because it results in the sacrifice of area.
A general object of an embodiment of the present invention is to provide a power mesh design which includes a bow tie shaped mesh.
Another object of the present invention is to reduce the number of vias which extend from the mesh structure.
Yet another object of the present invention is to increase the routing area available on the structure.
Still another object of the present invention is to provide a mesh design which includes a T-shaped mesh.
Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a bow tie shaped mesh for use in connection with an L-shaped mesh. The present invention also provides a T-shaped power mesh structure which provides advantages over the L-shaped power mesh structure.